COROLLIFLOR.E. 



595 



1 — 2 in each cell or carpel, erect. Fruit capsular, 1 — 4-cellecl, 

 with septifragal dehiscence. Embryo {fig. 973) large, curved or 

 coiled in a small quantity of mucilaginous albumen, with folia- 

 ceous crumpled cotyledons. 



Fig. 973. 



Fig. 971. 



Fig.. 972. 



Fig. 9ri. Flower of Great Bindweed (Cahjstegia 



{Convolvulus) septum). Fig. 972. Diagram of 



the flower, showing two bracts on the outside 



of the calyx. Fig. 973. Vertical section of 



the seed. 



Distribution, ^r. — They are chiefly found in the plains and 

 valleys of hot and tropical regions. A few occur in temperate 

 climates, but they are altogether absent in the coldest latitudes. 

 Examples of the Genera : — Convolvulus, Exogonium, Ipomsea, 

 Batatas. There are nearly 700 species. 



Troperties and Uses. — They are chiefly remarkable for the 

 presence of an acrid milky purgative juice in their roots, hence 

 the order includes some important medicinal plants. The 

 purgative property of the juice is due to a peculiar resin. In 

 the roots of other species this resin is either absent or in but 

 small quantity, and starch or sugar predominates, which renders 

 them edible. The seeds of some species are also purgative. 



Batatas edujis.— The root of this plant constitutes the Sweet-Potato, which 

 is largely used for food in many tropical countries. 



Convolvulus, Bindweed. — From the incised fresh root of C. Scainmonia, 

 the valuable purgative gum-resin called Scammony is obtained. This plant 

 is a native of Asia Minor, Syria, and Greece. The greater part of the 

 Scammony of English commerce is imported from Smyrna. The roots of 

 many other species also possess in a certain degree purgative properties ; as 

 those of our native species. Convolvulus (Calt/stegia) sepium, C.arvensis, and 

 C. Soldanella, &c. It is said that Con volvulus disseclus yields hydrocyanic acid 

 when distilled with water. It is one of the plants used for flavouring Xoyau. 



Exogonium purga.— This plant is a native of Mexico, near ChicanquiVco. 

 Its tubercular roots constitute the trae Jalap of the Materia Medica, so well 

 known as a purgative. Jalap is officinal in the British Pharmacopoeia. 

 (See Iponuea.) 



Jpomcea. — The roots of /. Orizahensis are sometimes fcamd intermixed 

 with true jalap. This spurious jalap is kno^^Ti in Mexico as male jalap, and 

 in English commerce as icoodij jalap or jalap icood, and on the Continent as 

 light or fusiform jalap. It possesses similar, although less powerful pro- 

 perties than those of true jalap. The roots of /. Turpethuin, Tnrpeth, wete 

 QQ2 



